How is the protest unfolding?

The walkouts began at 10:00 (10:00 EST is 14:00 GMT) across America’s time zones.

Organisers of the National School Walkout, who were also behind the Women’s March in January 2017 against Mr Trump’s inauguration, called on “students, teachers, school administrators, parents and allies” to take part.

“Parents have the right to send their kids to school in the mornings and see them home alive at the end of the day,” they say.

“We are not safe at school. We are not safe in our cities and towns. Congress must take meaningful action to keep us safe and pass federal gun reform legislation that address[es] the public health crisis of gun violence.”

Image copyrightReuters

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Students at Marjory Stoneman Douglas High School walked to the football field

In Parkland, families and supporters applauded as thousands of students slowly marched on to the Stoneman Douglas school football field.

School principal Ty Thompson called on them to stage the “biggest group hug”.

A large crowd of students from the Washington area gathered outside the White House holding signs reading “Protect People Not Guns” and chanting “Never again” and “Enough is enough”.

Students in Cherry Hill, New Jersey, stood in a heart formation to pay tribute to the Parkland victims.

Image copyrightReuters

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These students from Fiorello H LaGuardia High School in New York chanted “No more violence”

In New York, hundreds of students from Fiorello H LaGuardia High School – many dressed in orange, the colour of the gun-control movement – took to the streets of Manhattan.

“Thoughts and prayers are not enough,” read one sign.

New York Governor Andrew Cuomo also joined protesters for a symbolic “die-in” – lying down in a street in Lower Manhattan.

Encourage military veterans and retired police officers to become teachers

Improve background and mental health checks

In addition, a new federal commission on school safety will examine the age limit issue.

Chuck Schumer, leader of the opposition Democrats in the Senate, dismissed the White House’s action plan as “baby steps”.

When the state of Florida passed a gun control law which raises the legal age for buying rifles to 21, it was sued by America’s main gun lobby, the National Rifle Association, which argues that such curbs violate the US constitution.

Media captionShoes mark young victims of gun violence

In a separate incident, a teacher in California is believed to have accidentally fired a gun in a classroom on Tuesday, injuring a student.

Police said the teacher at Seaside High School, in Monterey County, had been taking a public safety class when he accidentally discharged the weapon into the ceiling.

Officials said one student was injured by either bullet fragments or ceiling debris and was taken to hospital for treatment

The teacher has been placed on administrative leave and the incident is being investigated, police said.